The present invention relates to the field of providing information over a network. More particularly, this invention relates to filtering data transferred between two networks based upon tags indicative of the content of the data.
The World Wide Web (WWW) is a fully multimedia-enabled hypertext system used for navigating the Internet. WWW may cope with any type of data which may be stored on computers, and may be used with an Internet connection and a WWW browser. WWW is made up of millions of interconnected pages or documents which can be displayed on a computer or other interface to the WWW. Each page can have connections to other pages which may be stored on any computer connected to the Internet.
WWW is based on the concept of hypertext which is very similar to ordinary text, except that for hypertext, connections to other parts of the text or to other documents can be hidden behind words and phrases. The connections to these hypertext are referred to as hypertext links, and they allow the user to read the document in any order desired. WWW also utilizes hypermedia which allows links to connect to not only words but also with pictures, sounds and any other data files which can be stored on a computer.
More specifically, hypermedia is a method of connecting data files together regardless of their format. The hypermedia links held on a given WWW page describes the location of the document which a WWW browser should display by using a Uniform Resource Locator (URL). URLs enable WWW browsers to go directly to any file held on any WWW server. URL is a naming system, typically consisting of three parts, the transfer format (also known as the protocol type), the host name of the machine which holds the file (may also be referred to as the WWW server name) and the path name to the file. The transfer format for standard WWW pages is Hypertext Transfer Protocol (HTTP). Standard Internet naming conventions are utilized for the host name portion of the URL. UNIX* directory naming conventions are utilized to indicate the path name of the file.
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A firewall is used to separate one network of computers from another. For example, a corporation that connects to the Internet and WWW may install a firewall to prevent users outside the corporation from accessing data stored on the computer network within the corporation. Additionally, the firewall can prevent users within the corporation from accessing data on the Internet and WWW.
For example, a firewall may be configured to allow certain machines to be reached and not others. The firewall may be further programmed to allow certain applications to pass through the firewall and to deny access to other applications. This provides a secure, but coarse level of access control for corporate Intranets.
A proxy sits on top of a firewall. A proxy looks at a higher level of the data transfer. It is typically a process that responds and acts on behalf of client requests. A proxy may be used to improve performance by caching data from previous retrievals. A proxy may look at the data requests from the users within the corporation and prevent requests from being sent out which have a particular keyword in the URL. This, for example, may be used to prevent the retrieval of sexually explicit material from the Internet by performing a search of the words of the URL in a dictionary having particular banned keywords.
A method of controlling data transfer between a first network and a second network of computers is described. Content description language received from the first network by the second network is parsed to determine tag information within the content description language. The second network of computers makes a completion decision as to whether to allow the transfer based on the tag information.
These and other advantages of the present invention are fully described in the following detailed description.